This invention relates generally to improvements in devices and procedures for artificial joint replacement (arthroplasty). More specifically, this invention relates to an improved intramedullary cement restrictor or bone plug for confining or restricting the placement of bone cement introduced under pressure into the medullary canal of a patient bone during arthroplasty surgery, such as a hip joint replacement.
Artificial or prosthetic joint structures are used extensively to repair or replace a patient joint, such as hip, knee and shoulder joints. The prosthesis typically comprises a biocompatible structure or structures such as a titanium or cobalt-chrome alloy with a size and shape for secure affixation to a surgically resected patient bone. In many cases, the prosthetic device includes an elongated stem for slide-fit placement into the exposed medullary canal of the resected patient bone, such as the upper end of a patient's femur in the case of a hip replacement. A bone cement, typically methyl methacrylate, is often introduced under pressure into the medullary canal to provide a positive and stable prosthesis attachment to the patient bone. The pressurized bone cement is intended to fill the interstices of bone structure in surrounding relation to the prosthetic device to result in optimum prosthesis fixation.
When pressurized bone cement is introduced into the medullary canal, it is necessary or desirable to use a restrictor or plug element to confine the cement to surrounding relation with the prosthesis, rather than to permit the bone cement to migrate distally through the medullary canal in a direction away from the prosthesis. In this regard, numerous restrictor or plug devices have been developed for this purpose, and are adapted to be installed into the medullary canal immediately prior to placement of the prosthesis and bone cement. However, such prior restrictor or plug devices have generally comprised solid structural bodies which tend to compress air within the medullary canal at the downstream side thereof during slide-fit placement. Such compression of air within the downstream medullary space can result in undesirable and potentially dangerous embolisms.
There exists, therefore, a significant need for further improvements in cement restrictors for use in orthopedic surgery, particularly wherein a cement restrictor is designed to vent the downstream medullary space during placement thereof, and thereafter to accommodate facilitated sealing of the vent path to maintain pressurized bone cement within the upstream medullary space. The present invention fulfills these needs and provides further related advantages.